Specifications

57
VISUAL
CHECK OF
THE BOARD
OK?
CORRECT
PROBLEM
4.2VDC AT
EMITTER OF
Q20?
CHECK VOLTAGE
REGULATOR
CIRCUITRY FOR
RX VCO
YES
YES
NO
NO
LOW OR NO POWER
AT PIN4 OF T2
ARE Q301 &
Q302 BIASED
CORRECTLY?
CHECK R306,
R307, R308, R309
& L304
IS THERE RF
OSCILLATION AT
COLLECTOR OF
Q301?
CHECK
RESONANT TANK
(C307~9 & L303)
AND FEEDBACK
(C312 & C315)
SET LOWEST
FREQUENCY
IS CONTROL
VOLTAGE(TP1)
BETWEEN 1VDC
AND 3VDC?
CHECK
RESONANT TANK
(C307~9 & L303)
IS KVCO
BETWEEN 6MHZ/V
AND 7MHZ/V?
REPLACE C303
IS RF LEVEL AT
C318 BETWEEN -3
& 0DBM?
IS D301DC
BIASED?
IF R302 & L301 ARE OK,
MAKE SURE
SYNTHESIZER IS
WORKING CORRECTLY
NO
NO
YES
YES
YES
NO NO
YES
IF L305, COUPLING CAP. (C311, 313,
318) AND FEEDBACK (C312 & C315,
L304, R309) ARE OK, REPLACE LOW
GAIN DEVICE(S)
YES
NO
NO
REPLACE OR RESOLDER
NECESSARY COMPONENTS
OF HARMONIC FILTER
(C28 ~ 32, L4 ~ 5)
IS RX BUFFER
STAGE WORKING
CORRECTLY?
ARE Q19
BIASED
CORRECTLY?
CHECK RX_5V
AND BUFFER
COMPONENTS
IF L14 AND
C100 ARE OK,
REPLACE Q19
YES
YESYES
NONO
Figure 9.4. Troubleshooting Flow Chart for RX VCO